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The unicodeSets accessor property of RegExp instances returns whether or not the v flag is used with this regular expression.
RegExp.prototype.unicodeSets has the value true if the v flag was used; otherwise, false. The v flag is an "upgrade" to the u flag that enables more Unicode-related features. ("v" is the next letter after "u" in the alphabet.) Because u and v interpret the same regex in incompatible ways, using both flags results in a SyntaxError. With the v flag, you get all features mentioned in the u flag description, plus:
Some valid u-mode regexes become invalid in v-mode. Specifically, the character class syntax is different and some characters can no longer appear literally. For more information, see v-mode character class.
Note: The v mode does not interpret grapheme clusters as single characters; they are still multiple code points. For example, /[🇺🇳]/v is still able to match "🇺".
The set accessor of unicodeSets is undefined. You cannot change this property directly.
| ECMAScript® 2027 Language Specification # sec-get-regexp.prototype.unicodesets |
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This page was last modified on Jul 10, 2025 by MDN contributors.
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